This very simple model provides a pressure drop which is proportional to the flowrate and to the opening input, without computing any fluid property. It can be used for testing purposes, when
a simple model of a variable pressure loss is needed.
A medium model must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.
The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.